1. Field of the Invention
The present invention relates to a contact tester for checking a contact between a slider and a disk of a disk device in order to evaluate mechanical properties and tribological properties of the slider and the disk.
2. Description of the Related Art
In a disk device, for example, a magnetic disk device for magnetically recording and/or reproducing information, a slider provided with a magnetic head is positioned to float above a recording/reproduction surface of a magnetic disk keeping substantially a fixed distance therebetween, to record/reproduce information on/from the magnetic disk.
In the development and manufacture of such a magnetic disk device, various types of test apparatuses are used to ensure the mechanical properties and tribological properties of the slider and the magnetic disk. One of such test apparatuses is a contact tester for checking a contact between the slider and the magnetic disk.
Japanese Laid-Open Publication No. 8-297816 describes a contact tester for checking a contact between a slider and a magnetic disk. Referring to FIG. 24, a conventional contact tester 2400 for checking a contact between a slider and a magnetic disk will be described. A magnetic disk 1 as a recording medium and a slider 2 together with an arm 6 supporting the slider 2 are mounted to the contact tester 2400. The slider 2 is provided with a magnetic head (not shown) for recording/reproducing information on/from the magnetic disk 1. The contact tester 2400 includes: a spindle 3 for holding and rotating the magnetic disk 1; a spindle driving circuit 4 for driving the spindle 3; a voice coil motor 7 as an actuator for moving the arm 6 and thereby moving the slider 2 attached to the arm 6 in a radial direction of the magnetic disk 1; and an actuator driving circuit 8 for driving the voice coil motor 7. The contact tester 2400 further includes: an acoustic emission (AE) or acoustic stress wave sensor 101 as a micro-vibration detection element mounted on the arm 6; a high bandwidth amplifier 20 for amplifying an output signal from the AE sensor 101, a filter 30 for filtering out a frequency component required for the contact test from an output signal from the high bandwidth amplifier 20; and an oscilloscope 50 for displaying an output signal from the filter 30.
The operation of the above conventional contact tester 2400 will be described. The magnetic disk 1 is rotated with the rotation of the spindle 3 at a speed as high as about 5,400 rpm, for example. The slider 2 has an air bearing surface facing a recording/reproduction surface of the magnetic disk 1, and floats above the magnetic disk 1 keeping a substantially fixed distance therebetween. The voice coil motor 7 moves the arm 6 and thus move the slider 2 in a radial direction of the magnetic disk 1. The slider 2 is normally positioned above the magnetic disk 1 by a fixed distance (e.g., about 20 to 50 nm) as described above. In other words, the magnetic disk 1 and the slider 2 are in a non-contact state with each other. Actually, however, the slider 2 often comes into contact with the magnetic disk 1 in such occasions as the start and stop of rotation of the magnetic disk 1 or due to attachment of dust on the slider 2, a configurational defect of the slider 2 and the magnetic disk 1, and the like.
In the conventional contact tester 2400 shown in FIG. 24, the AE sensor 101 as a micro-vibration detection element is mounted on the arm 6, for detecting acoustic emission (AE) or acoustic stress wave generated by a contact between the slider 2 and the magnetic disk 1. The output signal from the AE sensor 101 representing the detection result is amplified to an observable level by the high bandwidth amplifier 20. The amplified output signal is filtered by the filter 30 to remove a noise component, and the filtered output signal is observed using the oscilloscope 50. From the waveform of the output signal of the AE sensor 101 observed with the oscilloscope 50, the strength, duration, and the like of the contact between the slider 2 and the magnetic disk 1 can be evaluated.
The above conventional contact tester 2400 has the following problems. Since the AE sensor 101 is mounted on the arm 6, it detects, not only an AE signal generated in the vicinity of a contact point when the slider 2 comes into contact with the magnetic disk 1, but also a vibration of the arm 6 superimposed on the AE signal. It is not possible to separate an actual AE signal from a signal generated by the vibration of the arm 6. This makes it difficult to improve the precision of the measurement. Another problem is that the mounting of the AE sensor 101 on the arm 6 changes the inertia of the arm 6, causing a difference from an actual system where no AE sensor 101 is mounted. Moreover, since the AE sensor 101 is mounted on the arm 6 supporting the slider 2, it is difficult to evaluate the influence of the contact between the magnetic disk 1 and the slider 2 on the magnetic disk 1 with high precision.